Breathing apparatus



Aug. 9, 1960 P. w. FlTT 1 BREATHING APPARATUS Filed June 7, 1957 Laiin!BREATHING APPARATUS Peter William Fitt, West Hendford, England, assignorto Normalair Limited, Somerset, England Filed lane 7, 1957, Ser. No.664,889 Claims priority, application Great Britain June 16, 1956 3Claims. (Cl. 137-64 I 10,000 ft., in order to supplement the oxygensupply in these rarefied regions, respiratory responsive members areoften employed to control the quantity of oxygen delivered to the mask.The actuation of these responsive members will open and close a demandor inlet valve, permitting oxygen to flow into the mask from a pressuresource. Up to 40,000 ft. the oxygen or a mixture of oxygen and air isgenerally delivered at a slight positive pressure to prevent leakage ofambient atmosphere into the mask so that the oxygen delivered by theregulator does not become diluted. At altitudes of 40,000 ft. or over,to prevent anoxaemia, the oxygen delivered at the mask must havesufficient pressure behind it to maintain oxygen tension in the lungsand to enable it to be absorbed by the blood to maintain an acceptableequilibrium level.

Regulators capable of providing these positive or safety presssures aregenerally provided with means whereby a positive pressure is exerted onthe respiratory responsive member controlling the demand valve to enableoxygen to be delivered to the wearer at sufficient pressure to maintainlung tension and to prevent air intake due to mask leakage. Such meansgenerally include systems employing aneroids, springs and levers. Adisadvantage of this arrangement is that very large loads areexperienced by the respiratory responsive member or diaphragm and otherworking parts when the regulator is working under high outlet pressureconditions.

It is accordingly an object of the present invention to providearregulator in which such excessive loads are substantially reduced.

Another object of the present invention is to provide a regulator whichat extreme high altitudes functions 1n a way which is comparable tonormal function at low altitudes.

A further object of the present invention is to provide a regulatoroperating on a principle which can be applied to any regulator able togive such positive pressures, and is such that instead of the very largeloads experienced by the diaphragm and levers when working under highoutlet pressure conditions, works in a way which is comparable to normalfunction.

The invention consists in a regulator having a respiratory responsivemember with one surface subjected to breathing pressure and the otheralternatively to ambient pressure or to pressusre greater than ambientpressure.

The invention also consists in a regulator as in the preceding paragraphwherein valve means are provided to vary the pressure on the side of theresponsive member remote from a breathing chamber, the valve meansincluding a pair of openatively coupled valves.

The invention also consists in a regulator substantially as hereinafterdescribed with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic drawing of a regulator embodying the presentinvention in one working position.

United States PatcritpfliO 2,948,292 Patented Aug. 9, 1960 fire I '2Figure 2 is a diagrammatic drawing of.the present invention analternative working position.

In carry g the'invention into fleet regulator generally indicated at 1is provided having a respiratory responsive member or diaphragm 2 whichoperates an inlet or demand valve '3 in response to inhalation andexhalation. Diaphragm 2 controls demand by way of inlet 6 to outlet 7which is connected to the wearers mask (not shown), outlet 7 being incommunication with a breathing chamber 8 through communicating port 9. Aclosed chamber 10 is provided opposite the breathing chamber side ofdiaphragm 2. Within chamber 10 a spring 11 provides a light loading ondiaphragm 2 in such a manner to ensure that the pressure in breathingchamber 8 .is maintained slightly higher than that in chamber 10.

At some convenient point which may be remote from regulator 1, a valvebody generally indicated at 12 is provided. Body 12 houses a pair ofvalves 13 and '14 attached to a common spindle 15. Valve 13 is springloaded by means of a spring 16 and valve 14 likewise by a spring 17. Ascrewed control knob 18 is provided to control the opening and closingof valves 13 and 14. A duct 19 with a reduced orifice 20 providescommunication with breathing chamber 8 and valve body 12 by way of valve13. A further duct 21 provides unrestricted communication betweenchamber 10 and a chamber 22 between valves 13 and 14 in valve body 12.Chamber 22 is adjacent a further chamber 23 which is in communicationwith the ambient atmosphere by way of duct 24. Thus, if valve 14 isopen, chambers 22, and 23 are in communication with each other and theambient atmosphere, at altitudes up to say 10,000 ft.

In operation, at altitudes up to say 10,000 ft., control knob 18 isadjusted so that valve 13 is in the closed position and valve 14 open(Fig. 1). Chamber 10 is then in communication with ambient surroundingsby way of duct 21, chambers 22 and 23 and duct 24. The regulator thendelivers oxygen to the mask at a pressure related directly to that ofambient pressure in response to movement of diaphragm 2.

At altitudes where a slight safety pressure is automatically obtainedfrom the regulator, or at any altitude where manual safety pressure isselected, and when for the aforementioned reasons greater pressures arerequired to be delivered by the regulator, control knob '18 may be soadjusted as to close valve 14 and open valve 13 (Fig. 2). Chambers 8 and10 are then placed in communication with one another and due to theslightly higher pressure in chamber 8 relative to that in chamber 10oxygenfiows through reduced orifice 20 in duct 19 to chamber 10 viachamber 22 and duct 21. Pressure in chamber 10 then builds up tending toequalise with the pressure in chamber 8, thus diaphragm 2 is subjectedto an increased surface pressure and the regulator operates as thoughthe ambient pressure were increased accordingly, until excess pressurein chamber is released by the opening of valve 14 against spring 17, theopening pressure being determined by the spring loading imposed. Thepressure in chamber 8 remains substantially constant thereafter due tothe restricting eifect of reduced orifice 20 and the constant pressurecontrolled in chamber 10.

I claim as my invention:

1. A demand regulator for breathable gas having a respiratory responsivemember controlling the demand valve thereof, said responsive memberhaving one surface subjected to breathing pressure and the other surfacesubjected alternatively to ambient pressure or to according to one Iconvenient form by way of example, an oxygen demand pressure greaterthan ambient, means providing such alternative pressure comprising firstand second operatively coupled valves, said first valve controllingcommunication between one side of said responsive member and the other,said second valve controlling communication between the side vof saidresponsive member remote from said breathing pressure and ambientatmosphere.

2. A demand regulator for breathable gas as claimed in claim 1 whereinas one of said operatively coupled valves is moved in a closingdirection the other of said operatively coupled valves is moved in anopening direction.

3. A demand regulator for breathable gas having a respiratory responsivemember controlling the demand valve thereof, said responsive memberhaving one surface subjected to breathing pressure and the other sur- ,4face alternatively to ambient pressure or to pressure greater thanambient, means providing such alternative pressure comprising first andsecond operatively coupled valves, said first valve controllingcommunication between one side of said responsive member and the other,said second valve controlling communication between the side of saidresponsive member remote from said breathing pressure and ambientatmosphere and adapted to relieve excessive pressure on the side of saidresponsive member remote from said breathing pressure.

References Cited in: the file of this patent UNITED STATES PATENTS2,755,799 Marty July 24, 1956

